Blast injury

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Background

  • Primary blast wave increased in closed space - detonation in corner has potential to increase blast yield to 8x
  • Recent enhanced-blast weapons (EBW) disperses gas before explosion - larger blast wave with lower pressure amplitude that diffuses around corners

Spalling Effect

Due to blast pressure forces, Injuries are to organs with air-fluid interfaces (spalling effect)

  • TMs
  • Alveoli
  • GI tract

Situational Examples

  • Military - young healthy soldiers with body armor reducing thoracic/abdominal injuries but significant groin and lower extremity injuries
  • Civilian - children to elderly, higher rates of penetrating thoracic/abdominal injury

Injury Classifications

Classification
Blast Type Injury Cause Injuries Example
Primary Direct effect from shockwave Sheer and stress forces TM rupture, Ocular Injury, concussion, blast lung
Secondary Penetrating trauma, amps, lacs
Tertiary Blast propels body or large object into body Crush injury and blunt trauma Similar to MVC: Fractures, Pneumothorax, Hemopneumothorax
Quaternary Environmental Burns, Toxins, Weather
Quinary Bodily absorption of contaminates Hypermetabolic state


Effects based on blast pressure[1]

Potential Injury Pressure (PSI) Structural Effects
Loss of balance/temporary ear damage 0.5-3 psi Glass shatters; facade fails
Slight chance of eardrum rupture 5-6 psi Cinderblock shatters; steel structures fail; containers collapse; utility poles fail
50% chance of eardrum rupture 15 psi Structural failure of typical construction
Lung collapse/damage 30 psi Reinforced construction failure
Fatal injuries 100 + psi* Structural failure

Clinical Features

Pulmonary

EENT

  • TM rupture most common - not a marker of PBI severity or prognosis
  • Hemotympanum
  • Ossicle injury
  • Direct ophthalmic injury, foreign bodies, or ophthalmic artery air embolus

Thoracic

  • Cardiovascular collapse (within seconds)
  • Hypotensiondue to impaired reflex that increases SVR

Infectious Disease

  • Transmission of disease due to penetrating trauma is rare but possible with HIV, HCV, HBV

Musculoskeletal

Markers of severe blast injury

  • > 10% TBSA burn
  • Skull, facial fracture
  • Penetrating injury to head or thorax
  • Traumatic amputations

Differential Diagnosis

Mass casualty incident

Evaluation

  • CXR, CT chest
  • FAST, comprehensive CT
  • Repeat clinical abdominal exams looking for peritonitis - X-rays, US, CT insensitive except in perforation
  • Initial CT head may not be enough - may require MRI for DAI
  • Labs
    • Consider carboxyhemoglobin and electrolytes
    • Screening UA for significant explosions
    • Burn labs (rhabdomyolysis, compartment syndrome, severe burns)
    • DIC labs (PT, aPTT, CBC, D-dimer, thrombin time, fibrinogen)
    • White phosphorous labs (hypocalcemia, hyperphosphatemia, LFTs)

Management

  • pRBCs and FFP in 1:1 ratio with platelets for hemodynamically unstable patients
  • TM rupture - initial treatment supportive and enough for 75% with spontaneous healing; operative repair may be necessary for others
  • Operative exploration for peritonitis
  • Air embolus (rare) - isolate air in apex of LV by placing patient in left decubitus, head down, feet up position

Disposition

  • Ambulatory patient with normal TM evaluation at low risk for occult blast injury - discharge with precautions
  • All others require admission

See Also

References

  1. Terrorism Handbook for Operational Responders by Armando Bevalacqua and Richard Stilp (1998) and the Department of the Navy EODB 60 A-1-1-4 (2001) “Table A-1 http://www.fema.gov/pdf/plan/prevent/rms/428/fema428_ch4.pdf

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